1. Field of the Invention
The present invention relates to a driving mechanism for a carrier that is movable in a reciprocating fashion relative to a main apparatus body, to a recording apparatus equipped with such a driving mechanism, and to a reading apparatus equipped with such a driving mechanism.
2. Description of the Related Art
In recording apparatuses that record images onto recording media such as paper based on image information using recording heads, or in reading apparatuses such as scanners that read originals, an image recording operation on a recording medium or a reading operation of an original can be performed by moving a carrier that carries a recording head or an image reading sensor in a reciprocating fashion within the main apparatus body. A driving mechanism of a known type used for moving the carrier includes a motor fixed to the main apparatus body, and transmission units such as a timing belt for transferring the driving force of the motor to the carrier. A driving mechanism of this type is equipped with a guide unit defined by a guide shaft fixed to the main apparatus body. The carrier is allowed to move in a reciprocating fashion along this guide shaft.
A guide unit such as this guide shaft has a rigid body having non-flexible and twist-resistant properties. If the guide unit and the transmission units are to be integrated, the transmission units will also have a rigid body. Giving the transmission units a rigid body can be problematic in that the transmission units on the main apparatus body side and the carrier side can possibly collide against each other with great force when the main apparatus body receives vibration or impact from the outside. This can possibly cause the transmission units to become damaged, dented, or deformed. To solve this problem, U.S. Pat. No. 6,022,091 discloses a driving mechanism for a carrier that employs a lead screw. In this driving mechanism, a protrusion provided on the carrier is brought into engagement with a helical guide groove of the lead screw, so that by rotationally driving the lead screw, the carrier can be moved in the axial direction of the lead screw. With this driving mechanism equipped with a lead screw, the carrier can be reciprocated with high accuracy.
When an apparatus equipped with this lead-screw-type driving mechanism is in a stopped state, such as when the apparatus is stored or is being transported, the protrusion on the carrier is positioned in engagement with a designated guide groove provided exclusively for the stop position. It is especially during this stopped state of the apparatus, such as when the apparatus is stored or is being transported, that the main apparatus body receives vibration or impact from the outside. Since none of the sections of the carrier during the stopped state of the apparatus are in contact with the helical guide groove located in the range where high accuracy movement of the carrier is required, damage, dents, or deformations rarely occur in this range even if the main apparatus body receives vibration or impact from the outside.
However, with the lead-screw-type driving mechanism described above, since the protrusion on the carrier is positioned in engagement with the designated guide groove for the stopped state, there is a possibility that a vibration or impact applied to the main apparatus body during transportation of the apparatus may cause the main apparatus body and the carrier to hit against each other through the protrusion. This can possibly cause the drive transmission units to become damaged, dented, or deformed.